Audio/video and data signal redistribution system

ABSTRACT

A system for redistributing a multiple input audio/video and data signals having a redistributing device equipped to receive signals in a multiple formats and redistribute a selected signal to a user&#39;s premises over conductors, preferably existing twisted-pair telephone wire. The redistributing device is in interactive communication with a communications interface located in the user&#39;s premises which receives user-input control signals and contains switching circuitry which routes the selected signal to the user&#39;s premises where it is received by the receiving unit such as a television receiver. A single redistributing device services an entire multi-user network from a common distribution point, and services multiple users independently. The system of the invention does not interfere with normal use of the telephone network, so users can interactively access services provided by the system and use the telephone at the same time. In one preferred embodiment the system of the invention dynamically allocates frequencies and modulation techniques to various output signals, to maximize spectral efficiency and minimize interference and cross-talk.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/522,940filed Mar. 10, 2000 now U.S. Pat. No. 6,567,981, which is acontinuation-in-part of application Ser. No. 09/127,963, filed Aug. 3,1998 now U.S. Pat. No. 6,038,425.

FIELD OF INVENTION

This invention relates to communications systems. In particular, thisinvention relates to an interactive audio/video and datatelecommunications system which integrates and redistributes audio/videoand data signals received in multiple formats to multiple users overexisting telephone wires.

BACKGROUND OF THE INVENTION

Modern society is heavily reliant upon many different kinds ofaudio/video and data telecommunications services affecting all aspectsof daily life. Television is one of the most popular sources ofinformation and entertainment. Other sources of information andentertainment include computer networks such as the Internet, whichtoday offers services such as interactive shopping, banking, gaming,venues for discussion and social intercourse and many other products andservices, home video games, video/DVD movie rentals, radio andtelevision broadcasts and the like. These types of services provide avirtually unlimited variety of information and entertainment topractically every corner of the world.

However, these services have evolved independently over many decades andas such are provided in different formats and through disparate channelsof distribution. For example, television signals can be received byoff-air antenna, cable redistribution networks (CATV) and satellitebroadcasts, but access to each signal source is independent of theothers and requires specialized equipment and/or service providers. Atelevision set can be equipped to receive signals from all of thesesources, but only one at a time so some form of switching equipment atthe receiving end is required to change the television signal source.Further, each of these signals itself comprises many channels, whichcomplicates attempts to pool the services into a single integratedsystem. The Internet is accessible by modem over CATV or telephonewires, but is typically connected to a computer which is a completelyseparate viewing system.

Prior to the invention there has never been a system available forintegrating these types of services, which would allow a user toinstantaneously access any channel provided by any telecommunications orbroadcast service using a single system. Moreover, prior to theinvention there has not been an inexpensive system available which isinteractive, simple to use and delivers any desired telecommunicationsand broadcast service over a single network of twisted pair telephonewires.

A new technology known as Digital Subscriber Line (DSL) is now availablewhich carries high-bandwidth data to subscribers over PSTN telephonelines using a form of fixed frequency Direct Multitone (DMT). Where thesubscriber is located in proximity to a telephone company which offersDSL service, data rates of up to 7 Mb/s are available, which permits thecontinuous transmission of video (including motion video) and audiosignals without interfering with telephony (voice) transmissions.

In conventional analog telephony the data rate is limited by filterswhich convert digital data streams to analog form suitable for PSTNtelephone transmission cables, which is very bandwidth intensive. InDSL, digital data is transmitted without conversion to analog, whichallows for a much wider transmission bandwidth in a signal that can beseparated from the analog voice signal. However, in order to accomplishthis over existing PSTN wiring, all existing digital-to-analog filtersmust be removed, which is a very expensive process, which increases asthe distance from the telephone company facility increases, and resultsin a high cost to DSL subscribers. Moreover, outdoor PSTN cable issubject to degradation, and any signal carried on outdoor wiring isvulnerable to ambient em interference and attenuation due to multipletaps and other connections. These factors combine to limit theusefulness of fixed frequency DMT.

It would accordingly be advantageous to provide a system for integratingbroadcast and telecommunications signals from a variety of sources,which can utilize conventional twisted-pair telephone wiring within asubscriber's premises and does not rely upon transmission to thepremises via outdoor PSTN cables utilizing dynamic frequency allocation(DFA). It would further be advantageous to provide such a system whichpermits interactive signal selection of virtually any type of broadcastor telecommunications signal by a user, and which maximizes definitionand minimizes interference by adaptively allocating bandwidth to signalsbased on the nature of the signal and its data content, amongst otherfactors.

SUMMARY OF THE INVENTION

The present invention provides an interactive audio/video and dataredistribution system which pools the various broadcast andtelecommunications services available to a user, integrating theseservices in a single system which redistributes audio/video and datasignals received in multiple formats to multiple users. The inventionallows each user to remotely select and control the audio/video or datasignal source desired to be viewed or accessed and provides access anyavailable broadcast and telecommunications system through a singlereceiving unit, in the preferred embodiment a television receiver ormicroprocessor appliance (MPA) such as a computer. Further, theinvention provides an interactive system which is simple to operate andallows the user to utilize interactive services such as those availableover the Internet. Still further, the invention can be implemented overexisting telephone wires, which considerably reduces the cost of thesystem and renders installation of the system easy and inexpensive.

The invention accomplishes this by providing a redistributing devicewhich is equipped to receive telecommunications signals in any desiredformat and redistribute selected signals to a user's premises. Theredistributing device is in interactive communication with an interfacelocated in the user's premises which receives control signals from theuser input using, in the preferred embodiment, a conventional infrared(IR) remote control device, and contains switching circuitry whichroutes the selected signal to the user's premises where it is receivedby the receiving unit, preferably a television receiver ormicroprocessor appliance (MPA) such as a computer.

A single redistributing device services an entire multi-user networkfrom a common distribution point for conventional telephone wire, andservices multiple users independently. Thus, in the preferred embodimentthe redistribution occurs within the users' premises or a central officeand is not reliant upon transmission across outdoor cable.

Moreover, the system of the invention does not interfere with normal useof the telephone network, so users can be interactively access servicesprovided by the system and use the telephone at the same time, or anyexisting off-air or CATV wiring, so users have the option of receivingservices over these networks as well.

Each user may select access to a telecommunications system or programfrom a menu-driven user interface, which may provide many levels ofsub-menus with options specific to the particular telecommunicationsservice selected by the user. The users within the network thus caninstantaneously and independently access any availabletelecommunications service regardless of the input signal format.

In the preferred embodiment the system of the invention is equipped withchannel lockout for parental control, optionally a signal processorwhich prevents videotaping of received programs, a magnetic card readeror other access control device, a system log which records allactivities and services accessed by users within the network for billingpurposes, a system override which allows the system operator to denyaccess to selected users of selected services, or redistribute selectedprogramming (for example a message in an emergency situation), and otherfeatures which will become apparent from the description below.

In the preferred embodiment, the system of the invention dynamicallyselects and allocates a redistribution frequency and modulationtechnique suitable for the particular service (signal) selected by eachuser. This may be based on such factors as interference from othersources, attenuation due to cable length (to subscriber premises) andcable type, signal-to-noise ratio, data density of the signal and signalsharing with other subscriber-selected signals being redistributed.

The system of the invention also permits multiple broadcasts to becarried within a single signal using suitable modulation techniques, forexample quadrature amplitude modulation (QAM). This allows the sametwisted pair to accommodate command signals, rebroadcast output signals,analog voice signals and data signals at the same time; and permits asingle subscriber to receive more than one broadcast ortelecommunications service at a time, superposed within a single signal,so that different receivers within a single subscriber premises canreceive different services.

One preferred embodiment of the invention is a browser-based system,according to which the selected signals are redistributed inbrowser-compatible format. This allows the system of the invention to beused with computers, either connected to a browser-adapted wall plate(using, for example, TCP/IP or open transport protocols), or within anintranet or local area network. In this embodiment redistributed motionvideo data signals are displayed by commercially available motion videohelper software, with or without associated audio, in compressed oruncompressed format.

The system of the invention also has the capacity to monitor, track andrecord subscriber usage for each broadcast or telecommunicationsservice, and to selectively block or enable specific services toindividual subscribers. The system may also include billing softwarewhich invoices subscribers based on usage of each service over anyspecified period.

The system of the invention thus integrates Internet, television,video-on-demand, telephony, data transfer, gaming, music-on-demand andT-commerce (television-based commerce) into a single interactive systemwhich can be made accessible to each unit within a building or complex,or alternatively to each subscriber within a local loop, all overconventional twisted-pair telephone wiring. Further, because the systemof the invention is connected to all broadcast and telecommunicationsservices, it can be used to reroute long distance telephone service toInternet telephony (VoIP and VOFR), with attendant cost savings to thesubscriber, and to route an Internet connection (eg. audio/video datasignals) to a computer or a television receiver with the appropriatesignal format.

The present invention thus provides a system for redistributing aplurality of audio/video and data signals over conductors, comprising aserver, and a redistributor for receiving a plurality of input signals,comprising for each input signal, a demodulator for demodulating thesignal, the server controlling an output channel selection of the inputsignal responsive to one or more control signals input into acommunications interface, wherein the redistributor dynamically selectsand allocates a redistribution frequency suitable for each output signalbased on one or more of: attenuation due to interference from othersources, attenuation due to cable length, signal loss, signal-to-noiseratio, data density of the output signal and signal sharing with otheroutput signals.

The present invention further provides a method of redistributing aplurality of audio/video and data signals to a plurality ofcommunications interfaces over conductors, comprising the steps of (a)receiving a plurality of input signals at a signal redistributor, (b)demodulating each input signal, (c) processing each input signal to aformat suitable for switching, (d) switching an output of theredistributor according to one or more control signals input into acommunications interface, (e) selecting and allocating a redistributionfrequency suitable for the output signal based on one or more of:attenuation due to interference from other sources, attenuation due tocable length, signal loss, signal-to-noise ratio, data density of theoutput signal and signal sharing with other output signals, and (f)routing the output of the redistributor to the communications interfacefor transmission to a receiving device.

In a further aspect of the invention the output signal comprises aplurality of superposed signals, whereby each of a plurality ofcommunications interfaces within a single subscriber premises is tunedto a different frequency so as to transmit to its associated receiverone of the superposed signals.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate by way of example only a preferredembodiment of the invention,

FIG. 1 is a block diagram of a redistributor according to the invention,

FIG. 2 is a block diagram of a communications interface for theredistributor of FIG. 1,

FIG. 3 is a diagrammatic illustration of a user interface,

FIG. 4 is a block diagram of a communications interface for a furtherembodiment of the redistributor operating on a single twisted-pairtelephone conductor, and

FIG. 5 is a block diagram of a redistributor adapted for thecommunications interface of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIG. 1, the invention comprises a redistributingdevice 8 and communications interface 100. The redistributor 8 serves asa telecommunications signal receiver and router/distributor, receiving aplurality of audio/video and data input signals and redistributinguser-selected signals to multiple users from the common distributionpoint of the telephone wiring at the multi-user site ortelecommunications office location. The communications interface 100 islocated in each individual unit and delivers the selected input signalfrom the redistributor to the receiving device 2, in the preferredembodiment a conventional television receiver or MPA, and receivescontrol signals input by the user for transmission to the redistributor8 to select the input signal and communicate interactively where theselected input permits. As used herein “audio/video and data signals”refers to all telecommunications and broadcast signals containingdigital or analog information which may comprise audio information,video information, data, communications protocol, or any combinationthereof.

The redistributor 8 receives signals in multiple formats, processes thesignals and, based on commands transmitted through the communicationsinterface 100, redistributes the selected signal to the user. Thecommand signals are transmitted to the redistributor 8, and the signalsare distributed to the users, over conductors which preferably comprisetwisted-pair telephone wire 1. In one preferred embodiment commandsignals are transmitted to the redistributor 8 on the voice (red-green)twisted pair, and redistributed signals are transmitted to the receiver2 on the unused (yellow-black) pair.

In rare cases where existing telephone wiring will not accommodate thisarrangement, for example in the case of a single pair cable,four-conductor twisted-pair cabling can be installed for the system ofthe invention or the building ground may be used as a common ground forthe redistribution and command signal pathways, allowing the inventionto operate effectively over a single pair of telephone wires, asdescribed in greater detail below. Alternatively, both the commandsignals and the redistributed signal(s) can be dynamically modulated ontop of the voice signals (typically at 4 to 7 kHz) and around thecommand signals (for example at 180 kHz) by suitable modulationtechniques, such as quadrature amplitude modulation (QAM), occupying anyunused frequency between the voice and command signal basebands and upto 1 GHz. In new buildings where the system of the invention iscontemplated in the building plans, eight pair cabling may be installed(instead of two or four pair cabling) to maximize the advantagesprovided by the invention, which would facilitate the servicing ofmultiple television receivers 2 in a single unit as described below.

The redistributor 8 is installed at a multi-user site, which may forexample be an apartment or condominium, commercial high rise, hospital,school, a local loop in a neighbourhood telephone system, a compound orcomplex containing many buildings, etc. The multi-user site may be anysite or network which provides a common distribution point forconventional twisted-pair telephone wire, for example PSTN, networkcategory five copper cable or any other local area network cabling,distributed to individual units within the site. Existing wiring in suchmulti-user sites is almost invariably, as a minimum, four-conductortwisted-pair copper wire distributed from a common distribution point toindividual units. Examples of multi-user sites are apartments buildings,office towers, hospitals, a block of detached houses networked in alocal loop, schools (through intercom wiring to individual classrooms),etc.

Each input comprises a demodulator and processor for the particularformat of the input signal. The preferred embodiment illustrated in FIG.1 incorporates various types of signal inputs by way of example only.The system of the invention may be equipped to receive and redistributeany video, audio, audio/video or data signal in any format, includingall remote audio/video and data signals and local audio/video and datasignals (such as a signal from a closed-circuit security camera orlocal- or wide-area network server), and the invention is not intendedto be limited to the specific types of signals illustrated and describedbelow.

Off-air input 20 is adapted to receive off-air television signalsthrough an antenna 22 configured to receive VHF and UHF frequency bands,including FM broadcast bands. The off-air signal is received by afrequency-agile off-air demodulator 24 with a tuner preferablycompatible with at least NTSC, PAL, and SECAM video formats, whichprocesses the separate audio and video signals to baseband for injectioninto off-air processor 26, which in turn processes the signals forswitching, as described below. The input frequency selection iscontrolled by commands transmitted by the user with a conventionalremote control through communications interface 100 to the server 6,which controls the cross point matrix switcher 7 through data buss A.

CATV input 30 is adapted to receive CATV signals through conventionalcoaxial cable 32. The CATV signal is received by a frequency-agile CATVdemodulator 34 with a tuner adapted to receive CATV signals throughoutsub, low, mid, hyper and super bands in both inter-harmonically relatedcarriers (IRC) and harmonically related carriers (HRC). The demodulator34 processes the separate audio and video signals to baseband forinjection into CATV processor 36 which processes the signals forswitching. The input frequency selection is controlled by commandstransmitted by the user through communications interface 100 to theserver 6, which controls the cross point matrix switcher 7 through databuss A.

DSS input 40 is adapted to receive DSS (direct satellite) signalsreceived by satellite dish 42 through a frequency agile DSS demodulator44, which processes the separate audio and video signals to baseband forinjection into the DSS processor 46. The demodulator 44 is preferablyadapted to receive the DSS signal in both C and KU bands, independent ofprotocol and format, with a tuner compatible with NTSC, PAL, and SECAMand a receiver bandwidth of approximately 0.900 to 21.8 GHz. Thedemodulator 44 processes the separate audio and video signals tobaseband for injection into DSS processor 46 which processes the signalsfor switching. The input frequency selection is controlled by commandstransmitted by the user through communications interface 100 to theserver 6, which controls the cross point matrix switcher through databuss A.

MMDS input 50 is adapted to receive MMDS (multi-point multi-distributionsystem) signals received MMDS antenna 52 through a frequency agile MMDSdemodulator 54, which processes the separate audio and video signals tobaseband for injection into the MMDS processor 56. The demodulator 54 ispreferably adapted to receive the MMDS signal in 2.4 GHz and 22 GHzbands, independent of protocol and format, with a tuner compatible withNTSC, PAL, and SECAM. The demodulator 54 processes the separate audioand video signals to baseband for injection into DSS processor 56 whichprocesses the signals for switching. The input frequency selection iscontrolled by commands transmitted by the user through communicationsinterface 100 to the server 6, which controls the cross point matrixswitcher 7 through data buss A.

MPEG input 60 is adapted to receive MPEG signals through MPEG decoderfor processing by demodulator 64, which processes the separate audio andvideo signals to baseband for injection into the MPEG processor 66. Thedemodulator 64 is preferably adapted to receive the MPEG signal in 1, 2or 4, for example from a video server or video library. The demodulator64 is independent of protocol and format, and has a tuner compatiblewith NTSC, PAL, and SECAM. The demodulator 64 processes the separateaudio and video signals to baseband for injection into MPEG processor 66which processes the signals for switching. The input selection iscontrolled by commands transmitted by the user through communicationsinterface 100 to the server 6, which controls the cross point matrixswitcher 7 through data buss A.

Graphics input 70 is adapted to receive component video signals from avideo source such as a video game server 72 for processing bydemodulator 74, which serves as a VGA or computer generated video andaudio signal to composite converter. Text, graphical user interfacesnavigation screens and video games and are separated into audio andvideo baseband signals for injection into the graphics processor 76which processes the signals for switching. The input selection iscontrolled by commands transmitted by the user through communicationsinterface 100 to the server 6, which controls the cross point matrixswitcher 7 through data buss A.

Internet input 80 is adapted to receive component video signals from acomputer 82 for processing by demodulator 84, which serves as a VGA orcomputer generated video and audio signal to composite converter.Internet browser and communications is not limited by protocol orarchitecture. Internet processor 86 processes the signals for switching.Navigation is controlled by commands transmitted by the user throughcommunications interface 100 to the server 6, which controls the crosspoint matrix switcher 7 through data buss A.

Closed-circuit input 90 is adapted to receive component video signalsfrom a closed-circuit camera 92, for example a security camera, forprocessing by demodulator 94, which serves as a VGA or computergenerated video and audio signal to composite converter. Closed-circuitprocessor 96 processes the signals for switching. Switching betweendifferent cameras is controlled by commands transmitted by the userthrough communications interface 100 to the server 6, which controls thecross point matrix switcher 7 through data buss A.

The server 6 is preferably an open architecture, platform independentand scalable computer having as a minimum a 486 microprocessor. Theserver 6 controls the upstream data from the communications interface100 and all demodulated inputs, and manages the database as describedbelow to provide accounting, billing, audit trails and programmehistory. The server 6 provides many communications ports for ISDN,fibre, satellite, PSTN, analog and digital input-output devices and/orany other desired accessory. The server 6 also functions as a router tocontrol and route information through the data busses A, B and C.

The demodulator data bus B interconnects all demodulators and decodersand interfaces to the server 6. The buss B is not limited to protocol,speed, frequency, form factor or format.

The processors 16, 26, 36, 46, 56, 66, 76, 86 and 96 process theirrespective incoming signals into a format that is able to be switched bythe cross point matrix switcher 7 and sent to the communicationsinterface 100 over unshielded twisted pair copper cable. The processors16, 26, 36, 46, 56, 66, 76, 86 and 96 each match the impedance of thesignal to the output impedance; raise the baseband of the demodulatedsignal (for example to 300 kHz); equalize the high frequency components(for example at 3 dB) and increase the level of chroma; and increase thepeak-to-peak voltage (vpp) of the demodulated signal. The processors 16,26, 36, 46, 56, 66, 76, 86 and 96 also convert and translate upstreamcontrol signals received by the cross point matrix switcher 7 from thecommunications interface 100 and route the control signals to the server6 via data buss B.

The cross point matrix switcher 7 is preferably a wideband multi-channelnon-blocking many-to-one switch, which is not limited by size,bandwidth, speed, form factor, protocol, architecture, format or cabletype. Control signals received by and output from the processors 16, 26,36, 46, 56, 66, 76, 86 and 96 are transmitted to the server 6, whichcontrols the cross point matrix switcher 7 and routes the selected inputto the output of the cross point matrix switcher 7 for transmission backto the communications interface 100. A separate cross point matrixswitcher 7 is provided for and dedicated to each communicationsinterface 100 installed in the individual units within the multi-usersite.

The processor data buss C interconnects all processors 16, 26, 36, 46,56, 66, 76, 86 and 96 and interfaces to the server/router 6. The buss Cis not limited to protocol, speed, frequency, form factor or format.

Data buss A interconnects each cross point matrix switcher 7 with theserver/router 6. The buss A is not limited to protocol, speed,frequency, form factor or format. The output of cross point matrixswitcher 7 is connected to a standard or custom telephone or twistedcopper splice block 5. Type Bix and no. 66 are typically used, howeverthe configuration of the splice block 5 does not effect the operation ofthe invention. The splice block 5 conveys the output of the cross pointmatrix switcher 7 to the copper pair (red-green) of the existingtelephone system or PSTN. The splice block 5 may also be used forcategory five or 10 baseT cabling.

The redistributor 8 may also include an HDTV processor 144 forprocessing HDTV signals received at HDTV input 140 by an antenna,satellite dish or other suitable receiver 142. The HDTV processor 144 isconnected directly to the server 6, which controls the channel selectionand routes the HDTV signal through a high speed data router or hub 150that distributes HDTV signals from the server 6 over coaxial cable orcategory five or six cable (10BaseT) network within the multi-userenvironment. Utilizing DFA and selective modulation techniques, theoriginating HDTV 8VSB signals may be down-converted to base band fortransmission on existing PSTN wiring from the redistributor 8 to thecommunications interface 100. Alternatively, the 8VSB signal may beconverted by other complimentary modulation techniques such as (but notlimited to) QAM, QPSK, PSK and the like, for redistribution over PSTNwiring from the redistributor 8 to the communications interface 100 forre-emulation to HDTV standard. If category five or six cable (whichtypically has 4 pairs) is used, the HDTV signal requires only two pairsand the two unused pairs of the category five or six cable may becoupled to the PSTN splicer block 5, as shown in FIG. 1, to effectivelymerge the telephone wiring (red/green and yellow/black) with the unusedpairs in the category five or six cable.

Additionally, a movie storage database 146 may be connected directly tothe server 6, which controls the movie selection responsive to controlsignals input by the user based on a directory accessed by the userthrough a movie sub-menu.

The audio/video and data signals output by the redistributor 8 may betransmitted to the communications interfaces 100 in the individual unitsover both used and unused pairs of the PSTN. The PSTN is not limited byvoltage or frequency, and can transmit the full bandwidth of audio/videoand data signals over a considerable distance with minimal signal loss.The communications interface 100, illustrated in FIG. 2, may be aself-contained wall plate with one or more RJ11 ports, or alternativelymay be a separate external device which plugs into the RJ11 port of aconventional telephone wallplate and provides, as desired (but notlimited to), one or more RJ11 ports, F connectors, RJ45, compositeaudio/video (RCA) ports, component video ports, firewire ports, and/oruniversal serial bus (USB) ports for the receiver 2 and optionally abypass port for the telephone.

At the communications interface 100, illustrated in FIG. 3, the modifiedcombination of the signals are received from redistributor 8, andaudio/video signals are separated into individual audio and videosignals by separator 102. In the preferred embodiment the video signalranges from DC to 4.5 MHz NTSC, PAL or SECAM, and the audio (analogtelephone) is a sub-carrier ranging between (but not limited to) 4.6 to5.0 MHz, preferably around 4.7 MHz.

The output of the separator 102 is fed into the audio and videodemodulators 104, 106, respectively. The video output of the separator102 is preferably at an impedance of 75 to 100 ohms, depending on lineconditions and the setting of the video modulator in the redistributor8, which will compensate for any mismatch loss and common moderejection. The video signal may be reshaped to clip the H sync andcolour burst peaks using a horizontal synchronization attenuator andamplifier that is controlled by the redistributor 8, to regulate thesync level to the receiver 2 so that illegal recording of video may beprevented (a typical television receiver is able to lock to the videosignal with as little as 15 units of sync, whereas videotape recordersgenerally require a minimum of 25 units of sync to lock effectively tothe input signal).

Optionally a signal-to-noise detector can be provided in thecommunications interface 100, which signals the redistributor 8 to boostthe signal output level if the signal-to-noise ratio decreases below athreshold level. This would allow the redistributor 8 to compensate forthe disparate length of telephone cable between the splicer block 5 andthe communications interfaces 100 in the various individual units (forexample, a penthouse apartment will experience less attenuation from aroof-mounted redistributor 8 than a basement apartment located withinthe same multi-user site). It is also contemplated that a systemanalyzer for testing the various signals used by the system would plugdirectly into the RJ11 port in the communications interface 100, andcould communicate directly with the server 6 for recording systemanalysis results.

The video demodulator 104 then converts the reshaped video into astandard composite video signal at 1 vpp for injection to the modulator110. The demodulator 104 also filters common mode rejection and otherradio frequency and electromagnetic interference. The modulator 110modulates the video signal to a selected channel such as channel 3 usingconventional NTSC, PAL, or SECAM modulation techniques. The modulator110 is preferably phase lock looped with saw filtering, and frequencyagile within the 1 GHz bandwidth spectrum. The communications interface100 may be provided with a user-operated switch (not shown) forselection of channel 3 or 4, which is standard for domestic videoreceivers.

The output of the modulator 110 is connected directly to the receivingdevice 2. In the preferred embodiment the receiving device 2 is atelevision set, however it may be a videotape recorder, stereo receiver,MPA or any other device capable of receiving an audio/video or datasignal.

The audio sub-carrier signal is received from the output of theseparator 102 and demodulated (stereo on monaural) by audio demodulator104 to a common audio base band signal of approximately (but not limitedto) a 20 Hz to 20 kHz frequency range with an impedance which can varyfrom 75 to 600 ohms, for injection to the modulator 110 and optionallydirectly to an audio output. The demodulator 104 also filters out radiofrequency and electromagnetic interference.

The data modulator 120 sends instructions from the interfaces upstreamto the redistributor 8, receiving a varying data stream from one of aplurality of interfaces, which preferably includes an optical interfacesuch as an infrared receiver 122 comprising a photoreceptor thatreceives signal from a common hand held IR remote control device 123.The remote control 123 is used to input numeric information whichcontrols the signal input selection, and the channel selection where theinput signal includes multiple channels (for example a CATV televisionsignal). The IR receiver 122 may be built into the communicationsinterface 100, or may be wired to the communications interface 100remotely and mounted at a convenient position such as on the televisionreceiver 2. In the preferred embodiment the remote control device 123will control the power, mute and volume, and picture/sound settings ofthe television receiver 2 directly through the television receiver's IRremote system. All other selections are controlled by the redistributor8 based on control signals input by the user into the infrared receiver122 using the remote control device 123, and transmitted to theredistributor over live (ring and tip) PSTN wiring.

The communications interface 100 may also include a data port 124 forinterfacing with other types of data entry devices, for example akeyboard, a mouse, track pad and/or joystick, a bar code and/or swipecard reader, and any other data input device which facilitates the inputof alphanumeric information for purposes of interactivity. The data port124 is not limited by protocol, standards, speed, clock or voltage.

The data modulator 120 is preferably also inductively coupled, or directcapacitively coupled, to the PSTN telephone connection as at 132. Thecommon PSTN is passed directly onto the user without compromise so thattelephone, facsimile and Internet functions all operate normally. Themodulation scheme is selected according to the upstream datarequirements. FSK has been found to work favourably. The frequencybandwidth is variable and the frequency allocation is agile. A frequencyin the range of 160 to 190 kHz has proven effective and does notinterfere with telephone signals (which are typically in the range of300 Hz to 1.5 kHz). The data modulator 120 incorporates high and lowpass filters, and may operate at data rates ranging from 300 to 30,000bps or as otherwise desired. The circuitry of the communicationsinterface 100 may be programmed into an ASIC or like hardware.

The network card 132 is able to interface with any twisted pair wire,whether included in the telephone cable bundle or a separate categorythree, five, six or other cable. The network card is not limited to IEEE10baseT standards, preferably QAM, QPSK, PSK etc. The network card 132provides an optional interface for connecting client or server computersto the system of the invention. Any microprocessor-based appliance 134may be connected to the network card 132 and may include peripheralssuch as printers, scanners, modems etc. The network card 132 may beadvantageously employed in newer multi-user environments, where existingtelephone wiring typically provides at least three twisted pairs (oftenbetween four and eight pairs) in the PSTN cable.

In one preferred embodiment information input into the communicationsinterface 100 using these upstream devices is transmitted to theredistributor 8 over the red/green pair of the telephone cable, which isused for the ring and tip lines of the telephone service. These controlsignals are preferably transmitted in a data carrier having a frequencyof approximately 180 kHz. The content of the control signals issufficiently sparse as to require very little bandwidth, and the signalis preferably filtered so as not to interfere with the telephoneservice. The ring/tip twisted pair may be used to provide the powersupply for the communications interface 100, or if insufficient power isavailable from the telephone service the communications interface 100may be powered directly from a transformer (not shown) in theredistributor 8 outputting a DC signal along with the redistributedoutput signal over the yellow/black twisted pair.

Interactivity using the remote control 123 or other infrared devicepermits the user to utilize such services as shopping, banking andelectronic commerce, gaming etc. which are presently available over theInternet. It is also possible to transmit audio/video and data signalsover the yellow/black PSTN without interfering with the incoming videosignal. This would increase the level of interactivity and permit suchcomplex data exchange functions as video conferencing.

In the preferred embodiment for connection to a multiple-pair PSTNnetwork a plurality of carriers are established using modulationtechniques such as frequency division multiplexing, orthogonal frequencydivision multiplexing, QAM, FSK, PSK, QPSK etc. as follows: DC to 4.5Mhz for video data signals; 4.55 Mhz for serial audio (BTSC stereoaudio) signals; 8.5 to 12 Mhz for high speed data signals; and 12 to 13Mhz for voice data. Carriers at higher frequencies experience higherlosses due to attenuation, em and rf interference, so in this embodimentthe voice carrier is preferably constrained to a narrow bandwidth tominimize losses. Other bands may be selected as may be suitable forvarious available modulation techniques. Spread spectrum transmissionmethods conventionally used on AC power lines can also be used toprovide signals for extra voice and data lines, a printer port,pay-per-use software etc.

To install the system of the invention, the redistributor 8 is locatedat a multi-user site in the vicinity of the common distribution pointfor the telephone wiring at the site. This may for example be a mastertelephone panel in a commercial office tower, apartment building orhospital, a local loop distribution box in a residential neighbourhood,etc. The output of the cross point matrix switcher 7 is connected to thePSTN yellow/black pair, or any other unused twisted pair in the PSTNcable, for transmitting the selected input signal to the communicationsinterfaces 100. The input to the cross point matrix switcher 7 isconnected to the red/green pair (or equivalent ring and tip conductors)in the PSTN cable, for transmitting control signals from thecommunications interface 100 to the redistributor 8.

One or more communications interfaces 100 are installed in theindividual units within the site. Each communications interface 100provides at least a remote control interface such as an opticalinterface 122 connected to the red/green PSTN, and an output forconnection to the receiving device 2, such as a conventional 75 ohmcoaxial connector, connected to the yellow/black PSTN. A network card132 is optionally connected to a second unused pair in the PSTN cablefor interfacing with a personal computer, microcomputer or computernetwork 134.

The system may be managed by a service provider, who can either pay thevarious input signal providers (where the input signal is a fee-basedservice) and charge the individual units a fee for use of the system, orbill the individual units for payment directly to the signal providers.The server 6 maintains a database through which all input signal andchannel selections input by users in the multi-user site are tracked andrecorded for billing purposes. This information can also be used bysignal providers to produce viewership and other statistical and relatedinformation. The system of the invention thus has the capacity tomonitor, track and record subscriber usage for each broadcast ortelecommunications service, and to selectively block or enable specificservices to individual subscribers. The system may also include billingsoftware which invoices subscribers based on usage of each service overany specified period.

The service provider preferably has the ability to insert or substituteprogramming into any output signal at any time, for example commercialmessages, emergency broadcasts or the like, through a signal overrideresident in the server 6.

The service provider may also bundle the telephone service with otherservices, for example to resell long distance telephone services througha dedicated port. A single twisted pair telephone cable is capable ofcarrying multiple voice, video and data lines, and could service manylines and extensions in the unit. The reselling scheme could includepay-per-use telephone services and any other telephone reselling scheme.

In the preferred embodiment the cover plate for the communicationsinterface 100 provides contact switches which disconnect when the coverplate is removed, providing an immediate indication that the system isbeing tampered with to prevent attempts to pirate signal services.

In use, the receiving device 2, preferably a conventional televisionreceiver, is maintained on channel 3 or 4 as optionally set by the user.When the television receiver 2 is turned on the redistributor defaultseither to a main menu or to the last input signal selected by theparticular user. An example of a main menu for the preferred embodimentis illustrated in FIG. 3. Each menu option provides a correspondingnumerical selection parameter which is selected by the user via theremote control 23. The user selects their choice of input signal byentering the corresponding numeric selection into the remote control123. The numeric selection is received by the optical interface 122 anda corresponding control signal is transmitted to the redistributor 8over the red/green PSTN and transmitted to the server 6 via cross pointmatrix switcher 7.

The selected menu option may provide any number of levels of sub-menus.For example, if the “television” option is selected by entering thenumber “1” the server 6 may switch to a submenu offering the options“1—Off-Air”, “2—CATV”, “3—HDTV” and “4—DSS”. Using the same remotecontrol 123 the user selects the numeric value corresponding to thedesired selection, and is prompted to enter the channel number. The mainmenu, sub-menus and prompt messages are generated by conventionalbrowser software resident on the server 6. Selectable options may alsobe embedded in the vertical blanking interval of an incoming videosignal, accessible by depressing a “hot key” on the remote control 123when information (for example a web site URL) is displayed on thetelevision receiver 2.

The server 6 signals the cross point matrix switcher 7 via data buss Ato connect the selected input signal to the output of the matrix switch90, and the input signal is transmitted to the communications interfaceover the yellow/black (or other unused) PSTN. If the input signalcontains multiple channels, for example in the case of a televisionsignal, the server 6 controls a tuner in the corresponding demodulator14, 24 or 34 to pass the selected channel. The selected input signal maymodulated to channel 3 or 4 and transmitted to the individual unit to bereceived on the user's television receiver 2 through a conventionalcoaxial or other two-conductor cable 3. Alternatively, a port can beprovided for direct connection of the component video and audio to thetelevision receiver, to be viewed in a “video” mode, which wouldeliminate the need for an output modulator 110 in the communicationsinterface 100.

The capacity of the server 6 is selected having regard to the number ofindividual units within the multi-user site. The server 6 provides aseparate cross point matrix or digital matrix switcher 7 for eachindividual unit, and can thus independently transmit an input signal toeach unit irrespective of input signals selected by users in otherunits. The possible selection of input signals is limited only by thecapacity of the redistributor 8 to receive signals in any particularformat. Where an individual unit has more than one television receiver2, where the telephone cabling contains extra twisted pairs theredistributor 8 may be equipped with a separate matrix switcher 7 foreach television receiver 2 within the unit. Thus, an eight pair twistedcable can support up to four separate television receivers 2 in a unit,each television receiver using one pair for incoming and outgoingaudio/video or data signals and another pair for transmitting controlsignals to the redistributor 8. This capacity can be increased evenfurther by assigning an identifier number to each communicationsinterface 100 within a unit, and using the ring/tip telephone pair totransmit control signals to the redistributor 8 for all televisionreceivers 2 in the unit; the redistributor 8 receives the identifiernumber and routes the audio/video or data signal along the twisted pairassociated with the particular communications interface 100 soidentified.

Because the telephone wiring in an individual unit acts as a commondistribution point for that particular unit, a scaled-down embodiment ofthe invention could be used to allow for controlling signals received bya television receiver 2 in the unit. For example, the redistributor 8might receive off-air, closed-circuit and CATV signals transmitted tothe unit by coaxial cable and 300 ohm wires, and when coupled to thetelephone wiring in the manner indicated above a television receiver 8can be switched remotely from one signal input to another.

In a further embodiment of the invention, communication occurs betweenthe redistributor 8 and the receiver 2 over a single pair of telephonewires. In this embodiment the building ground conductor is used as acommon ground for the redistribution and command signal conductors. Inthis embodiment redistributed signals are transmitted to the receiverover the ground and one of the ring/tip conductor pair, for example thering conductor, and command signals are transmitted to the redistributor8 over the ground and the other of the ring/tip pair, in this examplethe tip conductor. The ground differential can be compensated by DCrestoration using an op amp to cancel any 60 Hz AC signal hum generatedby the building power supply conductors. This embodiment isadvantageously employed in older buildings which may have only a singlepair of existing telephone wires, to thus avoid the need to install newwiring in order to implement the system of the invention.

FIG. 4 illustrates a communications interface 200 for a furtherembodiment of the invention operating over a single-pair PSTN network,or a single twisted pair of a multi-pair cable, with no reference toground. Rebroadcast signals transmitted from the redistributor,illustrated in FIG. 5, are thus sent to the communications interface 200over the ring and tip conductors, or any unused twisted pair in the PSTNcable. To accommodate the superposition of several signals onto the PSTNpair, input broadcast and telecommunications signals are re-modulatedand dynamically allocated to selected frequencies within theredistributor output signal bandwidth.

For example, in the embodiment of FIG. 4 a plurality of carriers may beestablished as follows: DC to 7 kHz for voice; any available frequencyfor command signals; and 200 kHz and higher for video data signals,serial audio (BTSC stereo audio) signals, high speed data signals,voice/fax data and other digital signals. In this embodiment suitablemodulation techniques such as QAM, FSK, PSK, QPSK etc. are employed tomodulate the higher frequency output signals. To avoid interference and“cross-talk”, in the preferred embodiment the system of the inventiondynamically selects and allocates a redistribution frequency, andpreferably a modulation technique/bit pattern, most suitable for theparticular signal selected by each user.

FIG. 5 illustrates a redistributor for the communications interface 200of FIG. 4, which modulates the redistributor output via any suitablemodulation technique, preferably selected in the manner described below.As in the previous embodiment the redistributor may be equipped toreceive and redistribute any video, audio, audio/video or data signal inany format, and representative inputs are shown by way of example only.The signal output of each demodulator is digitized by ananalog-to-digital converter 199 and fed to a frequency-agile modem 195capable of modulating the signal by QAM, QPSK, PSK, FSK, or any othersuitable modulation technique. A memory 198, for example a frame store,is provided to conceal anomalies in the redistributed signal caused bymomentary interruption of the input signal.

Processor 197 controls the modem 195 and sweep generator/spectrumanalyzer 194, which pulses the PSTN line out at multiple frequencies,either when a new signal is selected by the user or preferably on acontinuous basis, generating data representing the signal-to-noiseratio, carrier-to-noise ratio, attenuation, bits-to Hertz and as desiredany other RF parameters of the input signal, for optimization offrequency allocation and selection of an appropriate modulationtechnique by the redistributor. Processor 197 controls the operation ofthe sweep generator/spectrum analyzer 194, analyzes data generated bythe sweep generator/spectrum analyzer 194, and selects the frequency andmodulation technique for the signal in the manner described below.

The rebroadcast signals received by the communications interface 200 areinput to carrier detect/failure bypass 212, for example a solid statenormally-closed double pole double throw relay, which monitors the inputsignal for a carrier at a designated frequency and if the carrier is notpresent diverts the PSTN signal to PHONE 1 to restore normal use of thePSTN line by telephone 1. In normal operating mode, i.e. with theredistributor output carrier present, the signal is fed to sweepgenerator/spectrum analyzer 214, which (like the redistributor's sweepgenerator/spectrum analyzer 194) pulses the PSTN line in at multiplefrequencies, preferably on a continuous basis, to assess RF parametersof the input signal. The processor 240 controls the operation of thesweep generator/spectrum analyzer 214, analyzes data generated by thesweep generator/spectrum analyzer 214, and where a signal anomaly isdetected signals the redistributor to reallocate the signal.

It is possible to program the system so that the processor 240 candynamically reallocate frequencies and change modulation techniques,however in the preferred embodiment only the redistributor's sweepgenerator/spectrum analyzer 194 selects the frequency and modulationtechnique for each redistributed signal, and the sweepgenerator/spectrum analyzer 214 in the communications interface 200merely signals the redistributor in the case of a signal anomaly.

All control and rebroadcast signals are processed within thecommunications interface 200 in the digital domain by digital signalprocessor 240, which may for example comprise a RISC or any othersuitable microprocessor. Processor 240 also processes the subscriber'sinfrared commands received via optical interface 122 to generate controlsignals which are modulated to a designated frequency by QAM (or QPSK,PSK or any other suitable other protocol) modem 216. These signals aresent to the redistributor via the PSTN twisted pair to be processed inthe manner described above.

The processor 240 outputs signal data to a frequency agile modem 230capable of modulating the signal via QAM, QPSK, PSK, FSK or any otherdesired modulation technique. FIG. 4 illustrates a communicationsinterface having two modems 230 by way of example, however thecommunications interface 200 may be provided with a separate modem 230for each receiver 2 in the subscriber's premises. Each modem 230 outputsa demodulated signal to an MPEG decoder 232 (preferably having adedicated memory 234 which conceals anomalies in the redistributedsignal caused by momentary interruption due to signal overcrowding,frequency reallocation etc.), which outputs the digital signal to thedata bus 202.

The processor 240 controls the modems 230 and receives data output byeach modem 230 for distribution to graphics browser HTML interface 235,which outputs a browser-compatible signal to the data bus 202 thatallows the video to be viewed on a microprocessing appliance such as apersonal computer 82 through network interface 83. On command, theprocessor 240 outputs digitized video data to local video storage 244,for example for time-shifting programming, video replay etc. In thepreferred embodiment the processor 240 also outputs the digitized videodata directly to the data bus 202 for communication to peripherals andconsumer electronic devices through a FireWire interface 204 or othercommunications protocol.

Telephony is preferably conducted through spread spectrum transceiver226, coupled to the output of carrier detect/failure bypass 212, toallow the use of any desired number of telephone extensions.

The allocation of frequency by the redistributor is based on aprogrammed priority, for example using a lookup table or fuzzy logicsubroutine, which may consider such factors as interference fromexternal sources, attenuation due to cable length (from theredistributor to the subscriber unit), signal loss, signal-to-noiseratio, data density of the signal and signal sharing with othersubscriber-selected signals being redistributed. As an example, afacsimile data signal redistributed to one user would ordinarily beallocated a lower frequency than a standard definition television signalbeing simultaneously redistributed to another user in the network; afull motion video high definition signal to a third user would beallocated an even higher frequency. In each case the redistributor“tunes” the respective communications interface 200 to the frequency ofthe redistributed signal using a signal frequency select pulse whichprecedes the redistributed signal. The communications interface 200 thusadaptively alters the reception frequency responsive to instructionsfrom the redistributor.

Moreover, this dynamic frequency allocation occurs in response tocommand signals from other units within the network. Where for example afourth user requests a high speed digital data signal for computernetworking, the redistributor reviews the existing signal distributionand, based on programming reflecting the factors referred to above andthe demands of the newly requested signal, may reallocate frequencies ofexisting output signals in order to accommodate the new signal withmaximum spectral efficiency. Similarly, where an external emr sourcearises which causes interference at frequencies in use by the system,the redistributor may switch the affected signals to other frequenciesto avoid the ambient interference. The redistributor may be programmedto take into account factors other than those previously indicated,which are referenced by way of example only.

In this embodiment the redistributor may also be programmed to select amodulation technique suitable for the output signal demands at anyparticular time, considering the above factors and also selecting a bitpattern for optimal performance (pathological signals may require largerbandwidth while pseudorandom signals typically require a narrowerbandwidth). As with frequency allocation, this process is dynamic andprovides an “on demand” architecture that makes full use of theavailable bandwidth, allowing multiple unrelated signals to besuperposed on a single carrier.

This allows the a single twisted pair to accommodate command signals,rebroadcast output signals and analog voice signals at the same time;and permits a single subscriber to receive more than one broadcast ortelecommunications service at a time, superposed on a single carrier andmodulated to different frequencies, so that different receivers 2 withina single subscriber unit can receive different services over the sametelephone line. The redistributor can tune different communicationsinterfaces 200 within the subscriber premises to different frequencies,and thus each communications interface 200 is tuned to the particularfrequency of the redistributed output signal corresponding to thecontrol signal received by that communications interface 200.

To install this embodiment of the system of the invention, theredistributor is located at a multi-user site in the vicinity of thecommon distribution point, and the output of the cross point matrixswitcher 7 is connected to the PSTN ring and tip conductor pair or othertwisted pair in the PSTN cable, as are the communications interfaces200. The input to the cross point matrix switcher 7 is also connected tothe ring and tip conductors or other twisted pair for transmittingcontrol signals from the communications interface 200 to theredistributor. In this embodiment the redistributor discriminatesbetween bandwidths allocated to command signals and other bandwidths, tothus accept commands from the user; likewise, the communicationsinterfaces 200 each comprise a high pass filter (stop band at 10 kHz)which transmits to the receiver 2 bandwidths allocated to redistributedsignals but not analog voice signals (which are fed through a bypass tothe RJ11 telephone port).

One preferred embodiment of the invention is a browser-based system,according to which the selected signals are redistributed inbrowser-compatible format. This allows the system of the invention to beused directly with computers, either connected to a browser-adapted wallplate (using, for example, TCP/IP or open transport protocols), orwithin an intranet or local area network. In this embodimentredistributed motion video, digital stereo sound, etc. signals candisplayed by commercially available helper software, in compressed oruncompressed format.

The data bus 202 thus distributes the signal from the redistributor,incorporating a plurality of broadcast and telecommunications servicesin the manner described above, to any suitable receiver 2 including abrowser-equipped computer 82. Standard television receivers 2 receive ananalog signal output from digital-to-analog converter 111, modulated tochannel 3 or 4 by modulator 110 as in the previous embodiment. Digitaland high-definition television receivers 3 receive a DTV or HDTV signaloutput from encoder 215. Computers 82 receive a digital graphicsbrowser-based signal through network interface 83, and peripheral orcomputer electronic devices receive a digital signal through FireWireinterface 204. The number and permutations of available signals andreceiving devices 2 are virtually unlimited in this embodiment of theinvention.

It will be appreciated that the communications interface 200 may bedesigned for direct connection to the PSTN network, as a recessed wallfixture or a wall-mounted fixture. Alternatively, the communicationsinterface 200 may take the form of a set-top box (STB) which isconnected to a standard telephone wall plate by any suitabletwisted-pair cable, in which case the infrared receiver 122 foraccepting infrared command signals from the user is preferablyintegrated into the STB as in the embodiment of FIG. 2.

The invention having been thus described by way of example of thepreferred embodiments, it will be apparent to those skilled in the artthat certain modifications and adaptations may be made without departingfrom the scope of the invention, as set out in the appended claims.

I claim:
 1. A system for redistributing a plurality of audio/videosignals to a plurality of units over conductors, each unit beingserviced through a common distribution point, each unit within theplurality of units having at least one communications interface, thesystem comprising a server, at least one demodulator for demodulating atleast one input signal, the server controlling an output programselection of the input signals responsive to one or more control signalscorresponding to each user-selected program input into one of the atleast one communications interfaces in one of the plurality of units,and at least one processor for processing the at least one input signalfor switching by one or more of matching an impedance of the inputsignal to an output impedance, raising a baseband of the signal,equalizing high frequency components, increasing a level of chroma,increasing a peak-to-peak voltage, optimizing frequency allocation, andselecting an appropriate modulation technique, and at least oneswitching device for routing the program selection using an internetprotocol or other communication protocol or combination thereof, theswitching device being controlled by the server and outputting an outputsignal containing the user-selected program, which output signal is sentonly to the at least one communications interface within the one of theplurality of units and not to others of the plurality of units,responsive to the one or more control signals input into the at leastone communications interface, wherein the at least one communicationsinterface in the one of the plurality of units receives the programselection for transmission of the user-selected program to at least onereceiving device in the one of the plurality of units.
 2. The system ofclaim 1 in which the communications interface includes a data interfacefor receiving data from a keyboard, joystick, card reader, bar codereader or other data providing device.
 3. The system of claim 1 in whichthe communications interface includes a network interface fortransmitting data from a computer as an input signal to the demodulator.4. A method of redistributing a plurality of audio/video signals to aplurality of units over conductors, each unit being serviced through acommon distribution point, each unit within the plurality of unitshaving at least one communications interface, the method comprising thesteps of (a) receiving at least one input signal containing a program,(b) demodulating the at least one input signal, (c) processing the atleast one input signal to a format suitable for switching by one or moreof matching an impedance of the input signal to an output impedance,raising a baseband of the signal, equalizing high frequency components,increasing a level of chroma, increasing a peak-to-peak voltage,optimizing frequency allocation, and selecting an appropriate modulationtechnique, (d) selecting a processed input signal for redistribution toone unit of the plurality of units using an internet protocol or othercommunication protocol or combination thereof, according to one or morecontrol signals corresponding to a user-selected program input into atleast one communications interface in one of the plurality of units, and(e) sending an output signal containing the user-selected program onlyto the at least one communications interface within the one of theplurality of units, responsive to the one or more control signals inputinto the at least one communications interface, and not to others of theplurality of units.
 5. The method of claim 4 in which the communicationsinterface includes a data interface for receiving data from a keyboard,joystick, card reader, bar code reader or other data providing device.6. The method of claim 4 in which the communications interface includesa network interface for communicating data from a computer as an inputsignal to a demodulator.